In modern mobile communication systems different mobile radio standards like Universal Mobile Telecommunications System (UMTS), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communication (GSM), and enhanced data rates for GSM evolution (EDGE) are used. Thereby the GSM standard is often referenced as second generation standard (2G), EDGE is referenced as a standard of generation 2.5 (2.5G) and UMTS is referenced as a third generation standard (3G).
Respective radio frequency (RF) signals are received and processed in a radio frequency unit which for example is used for down converting the radio frequency signals to base band (BB) signals. Such radio frequency units are in many cases implemented in a special integrated circuit. The data received by the radio frequency unit from an antenna are converted to digital signals which are transmitted to a base band unit for further processing. A function of the radio frequency unit can be controlled by the base band unit. It is furthermore possible that an interface between the radio frequency unit and the base band unit is realized as a digital interface. Such an interface is not restricted to transmit received (RX) data from a radio frequency unit to a base band unit but also to transmit data to be transmitted (TX) via a radio frequency unit between a base band unit and the radio frequency unit.
Respective base band units and radio frequency units can be able to operate within the GSM/EDGE standard or the UMTS standard or both the GSM/EDGE and the UMTS standard. In other words, various combinations of 2.5G mobile radio standards and 3G mobile communication standards are possible. A GSM/EDGE standard is also referenced as an enhanced general packet radio service (EGPRS).
For example, the DigRF working group released an interface standard called “DigRF dual mode 2.5G/3G base band RFIC interface standard”, version 3.09, short DigRF V3.09, which is incorporated herein by reference with its full content. This standard defines a digital serial interface between a base band integrated circuit (BBIC) and a radio frequency IC (RFIC) in both directions, working at a data rate of 312 Mbit/s.
When transmitting data over an interface between a radio frequency unit and a base band unit, it is possible that a time base for the transmitted data has to be defined and adhered to. Furthermore the radio frequency unit can receive radio frequency signals from two or more antennas or receiving paths respectively. The respective data of the different receiving paths can be transmitted to the base band unit separately. Although in this case it can be necessary to define a respective time base for the data to be transmitted over the RF/BB interface.